The polymerization of olefins, such as ethylene, propylene and other alpha-olefins is an important industrial process which is run on a huge scale around the world. Important factors in the polymerization process are the properties and cost of the polymer product which relate to the catalyst used in the process. The use of certain types of catalysts results in the presence of residue of catalyst components in the polymer product. In one type of polymerization process, the catalyst is prepared in situ. In other types of polymerization processes, the catalyst is fully or partially prepared before use in the polymerization process. A catalyst and its components (co-catalyst, modifiers, external electron donors, etc.) can be attached to a solid support material or the catalyst and its components can be added individually. This means that in certain types of catalyst systems, the catalyst components (co-catalyst, modifiers, external electron donors, etc.,) can be added individually to the reaction medium during the polymerization process. On the other hand, there are other cases in which the catalyst can be premixed with all its components during the catalyst preparation process resulting in the addition of one catalyst component to the reaction medium during the polymerization process.
The preparation of supported metallocene catalysts has previously been complicated and expensive. For example, the preparation of supported metallocene catalysts has required expensive and troublesome silica dehydration and aluminoxanes treatment during catalyst preparation. Procedures typically used for the preparation of silica supports such as spray drying or re-crystallization processes are complicated and expensive. Also, high calcination temperatures are required to remove water, which is a common catalyst poison. These steps represent a significant proportion of the preparation of the catalyst. In addition, the use of silica as a support results in the presence of support residue in the polymerization product, which can affect product processing and properties, such as optical properties.
Since the type of catalyst system used plays a major role in the polymerization process, the form and the physical properties of the catalyst system are important. For example, a solid catalyst system in the form of granules, often supported on silica or magnesium chloride, is usually used in gas phase and liquid slurry polymerization processes in order to reduce possible fouling of the reactor.
One of the objects of the present invention is to overcome the difficulties encountered in the prior art. The present invention provides a new development in olefin polymerizations. The supported metallocene catalyst system of the invention in which polyvinylchloride is used as a polymeric support can be used in both slurry and gas phase polymerization processes.